Samoylova E, Lippert H, Ullrich S, Hertel I V, Radloff W, Schultz T
Max-Born-Institut, Max-Born-Strasse 2a, D-12489 Berlin, Germany.
J Am Chem Soc. 2005 Feb 16;127(6):1782-6. doi: 10.1021/ja044369q.
The excited-state dynamics of adenine and thymine dimers and the adenine-thymine base pair were investigated by femtosecond pump-probe ionization spectroscopy with excitation wavelengths of 250-272 nm. The base pairs showed a characteristic ultrafast decay of the initially excited pi pi* state to an n pi* state (lifetime tau(pi pi*) approximately 100 fs) followed by a slower decay of the latter with tau(n pi*) approximately 0.9 ps for (adenine)2, tau(n pi*) = 6-9 ps for (thymine)2, and tau(n pi*) approximately 2.4 ps for the adenine-thymine base pair. In the adenine dimer, a competing decay of the pi pi* state via the pi sigma* state greatly suppressed the n pi* state signals. Similarities of the excited-state decay parameters in the isolated bases and the base pairs suggest an intramonomer relaxation mechanism in the base pairs.
利用激发波长为250 - 272 nm的飞秒泵浦-探测电离光谱研究了腺嘌呤和胸腺嘧啶二聚体以及腺嘌呤-胸腺嘧啶碱基对的激发态动力学。碱基对显示出最初激发的ππ态到nπ态的特征超快衰减（寿命τ(ππ*)约为100 fs），随后后者以较慢的速率衰减，对于(腺嘌呤)2，τ(nπ*)约为0.9 ps，对于(胸腺嘧啶)2，τ(nπ*) = 6 - 9 ps，对于腺嘌呤-胸腺嘧啶碱基对，τ(nπ*)约为2.4 ps。在腺嘌呤二聚体中，ππ态通过πσ态的竞争衰减极大地抑制了nπ*态信号。孤立碱基和碱基对中激发态衰减参数的相似性表明碱基对中存在单体内弛豫机制。
